1. Field of the Invention
The present invention relates generally to a method and apparatus for aligning sheets of material moving along a path of travel. More particularly, the invention relates to a method and apparatus for aligning sheets of material moving along a production line. Most particularly, the present invention relates to a method and apparatus for aligning glass sheets of generally rectangular or trapezoidal shape moving along a path on a production line with one of their ends or short edges leading.
2. Description of the Prior Art
It is common in producing automotive glass, such as windshields or back lights and the like, to have a piece of glass moving along a production line with its top or bottom edge (with reference to its installed position) perpendicular to the path of travel. A common path of movement is to have an automotive windshield moving along a powered roller conveyor, moving through a heating furnace, and moving to a bending station which bends the heated piece of glass between complemental mold sections to impart a desired curvature to the glass. It has been critical to properly align the glass sheets prior to their entry into the furnace so that they are properly aligned when they come into the bending station.
U.S. Pat. No. 4,895,244 discloses an apparatus for aligning glass sheets moving on a conveyor line prior to shaping on a bending apparatus. These sheets are oriented with their longitudinal axis transverse to the direction of travel, and alignment in a transverse and longitudinal direction is needed. A pair of vertically extending stops engages the leading (wide) edge of the glass sheet in front of the opening to the furnace. A pair of side pushers are actuated in a lateral direction to move into engagement with the opposed ends of the glass sheet to move it into a predetermined position.
While advancing glass sheets with their top or bottom edges as the leading edge was generally satisfactory, as were the means for aligning such sheets on the conveyor, advancing technology in the glass fabricating art has made it desirable to advance items, such as windshields or back lights, with their short or end edge first as the leading edge. One obvious advantage of this is the fact that a narrower and less expensive furnace can be provided. Another advantage is that alignment in only one direction is required.
While conveyors for advancing sheets of materials with their short edge as the leading edge are known, until the present invention there has been no satisfactory method of aligning these sheets with respect to a reference line or point before they enter the glass heating furnace. Thus, those skilled in the art continued to search for a satisfactory way of aligning such sheets.